Martin Donlon's PicoROM Turns a Raspberry Pi RP2040 Into a Gadget for Rapid Vintage ROM Development
Installed in place of a 27-series EPROM, the PicoROM can have its contents updated in-situ in less than a second.
Developer and vintage computing enthusiast Martin Donlon has released a Raspberry Pi RP2040-powered device aimed at making it easier to rapidly iterate projects relying on a physical DIP-packaged read-only memory (ROM) chip — by providing an emulated ROM chip you can update over USB in no time flat.
"The PicoROM is designed for prototyping and rapid iteration," Donlon explains of the device. "A new image can be upload in less than a second over the USB connection using a simple command line tool. If you have ever found yourself in a situation where your iteration loop requires you to pull a ROM from its socket, erase it, flash it and put it back in for every code change, then you are who this was designed for."
The PicoROM itself looks like a breadboard-friendly development board, with 0.1" pin headers to either side — though its USB Type-C connector is at a 90-degree angle to the board itself. The reason for that becomes obvious when you see the device in action: the board mimics the pinout of popular 27-series erasable programmable ROMs (EPROMs), and the vertical USB port means the cable doesn't foul any other components when placed into a socket.
"The PicoROM can emulate ROMs up to 2MBit (256Kbytes) in size and access times of 70ns," Donlon explains. "Its size allows it to fit into almost any ROM socket regardless of how crowded the board might be. It uses the standard JEDEC pinout for a 32-pin ROM so it will generally work anywhere something like a 27C020 EPROM would work."
Hardware design files and software source code for the project are available on GitHub under the permissive MIT license; fully-assembled units are available to buy on the Peanut Butter Retro Tindie store at $25 each.